This article studies the joint effect of political and economic inequalities on redistributive taxation and institutional quality. The theoretical model suggests that income inequality, coupled with political bias in favor of the rich, decreases redistribution and lowers institutional quality. The effect of the former is to increase productive investment, and the effect of the latter is to decrease it—with resulting ambiguous implications for economic growth. Testing these predictions empirically in a panel of countries, we find that inequality has a negative effect on both institutional quality and redistribution.